The objective of the research program is to determine the role of corrosion in the deterioration of dental amalgam restorations by investigating the mechanism of corrosion, the effects of corrosion on the properties, and by developing suitable testing methods. In the current year the fundamental processes involved in the corrosion of high copper amalgams will be investigated by metallographic and microanalytical examination of specimens simulating the structure of dental amalgam and corroded under controlled conditions. The relationship between corrosion and mechanical properties will be investigated in a study of the effects of compositions on both creep and corrosion of the matrix phases of dental amalgam. The effect of porosity on corrosion will be examined using gas adsorption techniques of measurement of the true surface area of amalgam specimens; the porosity will be varied by changing the condensation pressure and the mercury/alloy ratio. The specimens will be tested for the corrosion resistance and the data correlated with the porosity. The project also includes development of improved testing methods for the evaluation of the corrosion resistance of dental materials.